With the rack in the middle position, preheat the oven to 180 °C (350 °F). Butter two 20-cm (8-inch) in diameter springform pans. Line the bottoms with parchment paper.
In a bowl of a large food processor or in a large bowl, combine the flour, brown sugar, cocoa, baking powder and salt. Add the remaining ingredients and blend until the batter is smooth. If you make the cake in a bowl, blend with an electric mixer.
Pour the batter into the pans and bake for about 45 minutes or until a toothpick inserted in the centre of the cakes comes out clean. Cool slightly. Unmould and cool completely on a rack.
In a bowl, whisk all the ingredients with an electric mixer until the mixture is creamy and smooth. If you want the frosting to be as dark as the tree cookies, do not to overwhip the mixture as it might fade.1. Italian Meringue
In a small saucepan, bring the sugar, water and corn syrup to a boil and cook until a candy thermometer reads 113 °C (235 °F). Remove from the heat while you whip the egg whites.
In a bowl, beat the egg whites and cream of tartar with an electric mixer until soft peaks form. Pour the syrup over the egg whites, avoiding the beaters, beating continuously until the meringue is just warm and form stiff peaks.
Cut the cakes in half horizontally to get four layers. Spread three layers with approximately 250 ml (1 cup) of chocolate frosting. Stack, ending with the unfrosted layer. Frost the entire perimeter of the cake with the remaining frosting. Top with the meringue just before serving. Decorate pine cookies and sprinkle with icing sugar.
It is important to decorate the cake with the meringue and the cookies just before serving.